Preheat oven to 350°F. In a mixing bowl, combine the oats, oat flour, baking powder, sea salt, cinnamon, and nutmeg. Stir through until well combined. Add thepureed banana and vanilla (and chocolate chips or raisins, if using) to the dry mixture, and stir through until combined. Using a cookie scoop or spoon, place mounds of the batter (about 2 to 2 1/2 tablespoons) on to a baking sheet lined with parchment paper. Bake for 14 to 15 minutes, until set to the touch and a touch golden. Remove and let cool on pan for just a minute, then transfer to a cooling rack.  

Note: Use an immersion blender and a deep cup to puree your bananas (this is easiest, but a blender or small food processor also work). It produces a very liquefied mixture, not like what you can get through mashing.

Per muffin:
114 calories, 2 g fat, 0.3 g saturated fat, 12% calories from fat, 0 mg cholesterol, 3 g protein, 22 g carbohydrate, 4 g sugar, 3 g fiber, 136 mg sodium, 49 mg calcium, 1 mg iron, 2 mg vitamin C, 8 mcg beta-carotene, 0.1 mg vitamin E